The present invention generally relates to data processor systems, and more particularly to a user selectable data processor system implemented on a programmable logic device.
Microprocessors are one of the most versatile electronic devices used by engineers. Typically, a microprocessor is able to recognize and execute a predetermined set of instructions (e.g., add, compare, subtract, jump, etc.). Engineers can direct a microprocessor to handle different tasks by writing different computer programs using the same set of instructions. As a result, different types of products can use the same microprocessor by changing the associated computer programs.
Although a microprocessor can handle many different tasks, it does not mean that it can perform all the tasks efficiently. As an example, a microprocessor having instructions that can perform only integer operations can theoretically handle all kinds of arithmetic operations. However, it may be more efficient to use a microprocessor that has floating point instructions if a task involves a large number of complex computational operations. Similarly, a microprocessor only needs to have a small number of registers to perform most tasks. However, a large number of registers may speed up tasks involving databases and tables.
The design of a microprocessor involves many compromises. For example, a microprocessor that is hardwired to execute floating point instructions is much more complicated than one that can execute only integer instructions. As a result, the cost is higher. Thus, some microprocessor manufacturers market a low cost microprocessor that can execute integer instructions only and a higher cost microprocessor that is hardwired to execute both integer and float point instructions. Similarly, different kinds of microprocessors have different numbers of registers, addressing modes, etc.
This proliferation of microprocessors presents an opportunity and also a problem to engineers. On the one hand, it is good to be able to select different microprocessors to optimize the designs of various products in a company. On the other hand, it is a headache to maintain inventory of the various ICs if many microprocessors are used. Thus, for those companies that have many product lines, it may be difficult to make a choice between fewer inventory problems and better product design.
The above problems can be solved by having a single IC that can emulate, on demand, one of several commonly used microprocessors.
The IC of the present invention is a programmable IC. It contains a configurable instruction processing unit and a superset datapath unit. The instruction processing unit further contains a configurable microcode unit and a non-configurable sequencing unit. The programmable IC can be programmed so that the microcode compatible with a target microprocessor is installed in the configurable microcode unit. The datapath unit is a superset of the datapath elements of all the target microprocessors. As an example, the register files of the superset datapath unit contains the largest number of registers (of various data widths) used in the target microprocessors. Similarly, the arithmetic logic unit (ALU) in the IC is able to execute all the arithmetic and logic operations of all the target microprocessors. The microcode in the instruction processing unit will select the correct registers and ALU operations so as to emulate the corresponding target microprocessor.
The above summary of the present invention is not intended to describe each disclosed embodiment of the present invention. The figures and detailed description that follow provide additional example embodiments and aspects of the present invention.